DESCRIPTION: Considerable progress has been made in recent years toward the development of viral vectors for gene therapy for the treatment of disease. Gene therapy using the human Adenovirus (Ad) has proven to be a particularly exciting prospect. Ad is a particularly useful virus for human gene therapy for a number of reasons. First the genetics of the virus and functions of many viral proteins have been characterized. Second, the Ad genome is easily manipulated and recombinant virses are readily grown to high titers. Third Ad has a wide host cell range, and recombinant Ad vectors have been used to efficiently infect multiple cell types in culture and in animals. Fourth Ad has the ability to productively infect resting cells in culture and in the animal and effect efficient gene expression in quiescent cells. Finally, Ad only is associated with mild disease, and not with development of any human malignancy. Several disadvantages exist for the use of Adenovirus as a vector for long term gene therapy. First Ad elicits inflammatory and cytotoxic T cell responses directed against virus-infected cells resulting in immune clearance and extinction of expression of any foreign gene introduced by the recombinant viral vector. Second, Ad has no direct means to persist in infected cells for extended periods of time. The specific aims of the proposal are: 1) to develop recombinant adenoviruses that carry sequences from the adeno-associate virus (AAV) genome to direct the stable integration of recombinant viral DNA into the host chromosome for stable maintenance; 2) to establish an Ad helper virus system where packaging of the helper virus genome is specifically suppressed, while a recombinant adenovirus carrying a large foreign DNA insert for gene therapy will be efficiently packaged; and 3) to develop new adenovirus packaging vectors that will be useful for alternative strategies for recombinant vector production. It is also proposed to identify the trans acting packaging components to further the basic understanding of the mechanism of selective encapsidation of adenovirus DNA into virions.